Members of the epidermal growth factor receptor family (ErbB1/HER1, ErbB2/HER2, ErbB3/HER3, and ErbB4/HER4) are transmembrane tyrosine kinases that are activated by ligand-induced dimerization. (Schreiber et al., 1983 Journal of Biological Chemistry 258(2): 846-53; Ushiro and Cohen, 1980 Journal of Biological Chemistry 255(18): 8363-5). These receptors regulate cell proliferation, differentiation, and migration, and their abnormal activation is associated with a variety of human cancers. (Yarden and Sliwkowski, 2001 Nature Reviews Molecular Cellular Biology 2(2):127-37). Several cancer drugs (for example, Erlotinib) interact with the ATP-binding site of the EGFR kinase to halt tumor growth and increase apoptosis in cancer cells.
It is known that the EGFR kinase domain is activated after ligand-induced dimerization of the extracellular region of the receptor, although the underlying mechanism has remained elusive. Studies have shown that mutations in the catalytic domain of EGFR can either increase or decrease with the kinase activity of these proteins. (Chan et al., 1996 Journal of Biological Chemistry 27(37): 22619-23).
The epidermal growth factor receptor (EGFR/ErbB1/HER1) receives a stimulus in the form of an extracellular binding event and communicates this information across the cell membrane to effect diverse signaling outcomes (Lemmon et al., 2010 Cell 141: 1117-1134). When this communication is misregulated via overexpression or mutation, the signaling consequences are associated with a variety of human diseases, including cancer. Therefore, deciphering how EGFR conveys information across the cell membrane is essential to the understanding of its role not only in normal biology, but also in disease progression and therapeutic response (Lemmon et al., 2010 Cell 141: 1117-1134; Avraham et al., 2011 Nature Reviews Molecular Cell Biology 12: 104-117).
Activation of EGFR triggers multiple cascades of signal transduction pathways. EGFR contains at least six autophosphorylation sites that serve as docking nodes for a multitude of intracellular signaling molecules including adapter proteins and other enzymes. Therefore, rather than regulating a single linear pathway, activation of EGFR modulates entire networks of cellular signal transduction cascades. These signals affect both cell cycle progression/proliferation and apoptosis. Two signal transduction cascades that lie downstream of EGFR are the MAPK (mitogen activated protein kinase) and Akt pathways. In the MAPK pathway, EGFR activates the small GTP binding protein Ras to transfer cell growth signals through the Raf-MEK-ERK cascade, culminating in the regulation of transcription factors important for cell cycle progression.
It has been shown that the intracellular juxtamembrane segment plays a crucial role not only in receptor activation, but also in relaying the identity of the bound ligand to the cytosol (Scheck et al., 2012 ACS Chem. Biol. 7: 1367-76). Bipartite tetracysteine display was used to demonstrate that ligand binding to the EGFR extracellular domains is transmitted across the membrane into a defined dimeric helical interface within the juxtamembrane. Additionally, it was discovered that ligand identity is communicated to the cell interior through distinct juxtamembrane conformations. It was also discovered that the juxtamembrane segment plays a crucial role not only in receptor activation, but also in decoding and relaying extracellular signals to the cytosol.
Four EGFR inhibitors have been approved for use: Cetuximab (Mendelsohn, et al., 2000, J. Oncogene, 19, 6550; Prewett, et al., 1996, J. Immunother., 19, 419) is a monoclonal antibody that directly inhibits the binding of growth factors to the EGFR extracellular domain (Li, et al., 2005, Cancer Cell, 7, 301), whereas gefitinib, erlotinib, and afatinib (Ciardiello, F. 2000, Drugs, 60, 25; Lynch, et al., 2004, N. Engl. J. Med., 350, 2129; Plummer, et al., 2006, J. EJC Suppl., 4, 1731; Shepherd, et al., 2005, N. Engl. J. Med., 353, 123) are tyrosine kinase inhibitors (TKIs) that directly inhibit the binding of ATP to the intracellular catalytic domain (Yarden, et al., 2012, Nat. Rev. Cancer, 12, 553; Zhang, et al., 2009, N. S, Nat. Rev. Cancer, 9, 28). Other molecules in these two categories, including reversible and irreversible TKIs that inhibit the drug-resistant EGFR double mutant, are in clinical development (Solca, et al., 2012, J. Pharm. Exp. Ther., 343, 342; Li, et al., 2008, Oncogene, 27, 4702; Ohashi, et al., 2013, Cancer Res., 73, 2101A; Walter, et al., 2013, Cancer Discovery, 3, 1404; Ward, et al., 2013, J. Med. Chem., 56, 7025; Zhou, et al., 2009, Nature, 462, 1070).
There is a need in the art for novel inhibitors of EGFR. Such inhibitors would be useful for treating diseases caused by EGFR activation and constitutively active mutants. The present invention fulfills these needs.